How can I find out my current package?

If you're just a random program, you can do this to find out what the currently compiled package is: 

    my $packname = ref bless [];

But if you're a method and you want to print an error message that includes the kind of object you were called on (which is not necessarily the same as the one in which you were compiled): 

    sub amethod {
	my $self = shift;
	my $class = ref($self) || $self;
	warn "called me from a $class object";
    }